The underwater portion of a ship's hull must be painted with a paint which contains a substance that is toxic to marine organisms in order to prevent the growth of those organisms on the hull. The toxicant which is presently being introduced into the newer paint formulations is organotin, which is usually in the form of tributyltin or tripropyltin. These organotin toxicants are very efffective in their intended role, but they are highly toxic to man.
Even after the effectiveness of a paint which contains an organotin toxicant has been reduced to a very low level as an antifoulant (due to leaching out of the organotin toxicant), it is still very toxic to man. When the old paint is removed from a ship's hull, usually by sandblasting, the paint residue contains enough organotin to present a serious hazard. The paint residue must be disposed of like any other toxic industrial waste, which at present is by packaging it in steel drums and burying the drums in an approved disposal site.
Disposal in this way does not eliminate the hazard, however; if the drums leak and ground water gets into the paint residues, the toxicant can be leached out and it then contaminates the groundwater in that area. Thus burying the paint residues merely delays the onset of problems due to organotin contamination rather than curing the problem. It has been suggested that the organotin can be detoxified by roasting it in a furnace; this consumes energy, hence is wasteful. What is needed is a method of detoxifying the organotin toxicant that does not use energy or cause pollution problems of its own.